For many electronic devices, particularly small hand-held devices, there is a desire to make the devices as small as possible. This means that it is important for batteries used in battery-operated devices to also be as small as possible. At the same time, device users wish to minimize the frequency with which the batteries must be replaced. Consequently, there is an ongoing need to provide small batteries with higher energy efficiency. At the same time, minimizing the battery cost is a goal.
The energy efficiency of electrochemical battery cells can be maximized by minimizing the number of cell components and the volume of each to provide as much internal cell volume as possible for active materials and electrolyte. One approach has been to use a cell housing with electrically conductive housing members in direct contact with the cell electrodes as the battery terminals. A seal member such as a gasket or grommet is often used to electrically insulate the two battery terminals and provide a compressive seal therebetween. Examples of such cell designs are found in typical button and coin cells, as well as somewhat larger cells.
A common problem found in conventional metal-air cells is the bowing of the air electrode away from the base, commonly referred to as “doming” of the air electrode. Doming can be caused by inward radial forces on the edges of a metal screen or expanded metal current collector in the air cell, due to the tight fit of the current collector in the can to provide good electrical contact. The doming results in unused space within the battery cell which causes a loss of internal volume that could be used for active ingredients and may adversely affect leakproofness of the cell housing.
In view of the above, it is desirable to provide an electrochemical battery cell with an increased internal volume for the electrodes and electrolyte, having an air electrode assembly with reduced or eliminated doming. It is further desirable to provide for an electrochemical battery cell with excellent sealing characteristics and excellent leakage resistance.